Conrad Bain, known best as TV dad Phillip Drummond on "Diff'rent Strokes," has died, family sources tell TMZ. He was 89 years old.

Bain passed away Monday night in Livermore, California; the cause of death has not yet been released. Bain's daughter Jennifer tells TMZ, "He was a lot like Mr. Drummond, but much more interesting in real life. He was an amazing father.”

Born in Alberta, Canada (yes, Mr. Drummond was Canadian), Bain served in the Canadian army during World War II and studied acting in New York City alongside Charles Durning and Don Rickles. He found success as a stage actor and played innkeeper Mr. Wells on the '60s vampire soap "Dark Shadows" before finding his niche in TV sitcoms.

[Related: 'The Jeffersons' Co-Star Ned Wertimer Dead at 89]

Bain played Bea Arthur's sparring partner Dr. Arthur Harmon on "Maude" for six seasons, which led to his best-remembered role: kindly millionaire Phillip Drummond, who took two orphaned African-American boys from Harlem into his Park Avenue home on NBC's "Diff'rent Strokes." Debuting in 1978, "Strokes" ran for eight seasons and made a star out of precocious tyke Gary Coleman. But Bain was the moral center of the show, always there to help Arnold and Willis learn their lesson with some words of wisdom.

These days, "Strokes" may be best known for the tragic lives of its young co-stars. Bain's TV daughter Dana Plato (Kimberly) took her own life in 1999 after years of drug use, Coleman (Arnold) faced serious financial hardship before passing away in 2010, and Todd Bridges (Willis) battled drug addiction and legal troubles for years. Bain told interviewers he had trouble speaking about his TV kids' real-life issues because he cared about them so much. But Bridges has credited Bain with helping him straighten out his life in the 1990s.

When "Strokes" ended in 1986, Bain returned to theater -- although he did reprise his role as Mr. Drummond in the series finale of "The Fresh Prince of Bel-Air" in 1996. Since then, Bain has turned his energies toward screenwriting and enjoying his retirement. He is survived by three sons and one daughter.